Step 7Some results

Measuring dyes

As a first test, I decided to measure some samples of food coloring and methylene blue. I don't have a lot of data points because the stepper motor I'm using takes rather big steps, resulting in rather big wavelength-jumps.

Also, because the unit is not calibrated in any way, I have no way of telling exactly which wavelength I'm measuring at any point.
The only cue I have is the color of light, which can roughly be matched to an approximate wavelength.

As you can see, the results aren't all that bad, considering the very low number of measurements taken.
It's clear that the yellow dye does not absorb much light in the green/yellow wavelength region. The blue dye seems to absorb anything but blue, and the green dye has an affinity for blue and red light, letting green pass through.

Step 8Afterthoughts / possible improvements

Although I'm quite pleased with the results so far, some steps can be taken to improve the device.

• Using a stepper motor with very small steps (to increase control over the wavelength)
• Using a real diffraction grating instead of a CD (to improve the spectrum)
• Calibrating the device by sending light of known wavelengths through the detector
• ...

All in all, it's been a very worthwhile project and I will probably continue to work on it to try and improve the device as much as possible!

HAVE FUN BUILDING!!!